1. Field of the Invention
This invention relates to device-steering shaft assemblies and instruments embodying same, more particularly to video endoscopes comprising device steering means which allow an operating physician to view surgical sites from different angles.
2. Description of the Prior Art
Endoscopes and borescopes, which are telescopic instruments used to inspect cavities or openings or other selected sites, have found a number of applications in medicine and other technologies. In the field of medicine, the use of endoscopes permits inspection of organs or tissue for the purpose of facilitating the obtainment of biological specimens or the viewing of a surgical site for the purpose of facilitating the manipulation of surgical instruments so as to avoid or minimize invasive and traumatizing surgical procedures.
Endoscopes generally comprise an insertion portion in the form of a tubular shaft that is designed to be inserted into a patient. Older conventional endoscopes used in medicine contain an objective lens unit at the distal (forward) end of the insertion portion which transmits an image of the area forward of the objective lens unit to a remote eyepiece for viewing by the surgeon, the image being transmitted to the eyepiece via an image-forwarding means in the form of a relay lens set, or an optical fiber bundle unit. In more recent years, in place of the eyepiece and at least part of the image forwarding means, it has been preferred to provide a small size solid state electronic video imaging device, such as one employing a CCD chip, in the imaging plane of the objective lens unit, and applying the output of that video imaging device via a suitable electronic transmission system to a video monitor for viewing by a user. The combination of an objective lens unit and a solid state video imaging device constitutes a video camera, and an endoscope that utilizes a video camera is known as a video endoscope. With both types of endoscopes, a surgeon can view the displayed image and use the information conveyed by that image to manipulate the endoscope and also other surgical instruments that have been inserted into the patient via the same or another incision or opening in the patient's body. Video endoscopes also may be of the stereo variety so as to provide depth perception. Stereo video endoscopes comprise optical means for generating first and second optical images, and video imaging means for generating first and second electrical signals in response to the first and second optical images respectively.
The present state of the art of endoscopes prior to this invention is demonstrated by the following U.S. patent applications and patents: (1) copending application Ser. No. 08/722742, filed Oct. 1, 1996 by K. Hori et al; (2) U.S. Pat. No. 5,538,497, issued Jul. 23, 1996 to K. Hori; (3) U.S. Pat. No. 5,582,576, issued Dec. 10, 1996 to K. Hori et al; (4) U.S. Pat. No. 5,603,687, issued Feb. 18, 1997 to K. Hori et al; and (5) U.S. Pat. No. 5,662,584, issued Sep. 2, 1997 to K. Hori et al; and the prior art cited in said application and patents. To the extent necessary, the teachings of those patent applications are incorporated herein by reference thereto.
Originally the insertion portion of endoscopes had a generally rigid tubular construction and the endoscopes looked straight ahead. However, soon variants were developed having fixed angular deviations from straight ahead viewing, typically 30.degree.. Subsequently, endoscopes with flexible tubular insertion portions appeared. Some of these flexible endoscopes can be remotely steered, such as by cables which cause the flexible shaft to bend. However, existing instruments of this type have limited angular deflection capabilities and limited minimum radii of curvature.
In so-called minimally invasive surgery, an endoscope is used to visualize the operating field inside a body cavity while the surgeon manipulates instruments therein so as to perform the surgical procedure.
New recently developed minimally invasive endoscopic procedures, such as thoracoscopy, are making greater demands upon endoscopic orientation than existing instruments can practically provide. For instance, it is becoming necessary to look sideways (i.e., 90.degree.) or even retrograde (approaching 180.degree.). In conjunction with the need for a larger range of viewing angle, there is also the requirement that the tip of the endoscope be positionable within the body cavity so as to take full advantage of the larger range of viewing angle. For instance, if it is desired to view an organ from behind--that is, to extend the endoscope beyond the organ and observe its hidden surfaces in retrograde fashion--then positioning the endoscope for this purpose may be impossible with a rigid, straight shaft endoscope or with currently available flexible shaft endoscopes. It would be helpful to the physician to be able to configure the insertion portion of the endoscope in a manner advantageous for entry and positioning relative to the surgical site, and have the endoscope maintain that configuration until changed by the physician. It also would be of value to be able to vary the orientation of the video camera in different situations without being restricted by the physical construction of the insertion portion. A further consideration of this invention is that many commercially available endoscopes have been designed for particular procedures and are not suitable for use in other procedures.